The primary goals of this project are to determine the physiologic and pharmacologic roles of naturally occurring and synthetic corticosteroids in the regulation of cardiac performance. Studies will be undertaken with corticosteroids on isolated papillary muscles, isolated perfused hearts, and intact animals. Investigations will include direct effects of corticosteroids as well as interactions with other inotropic and vasoactive agents. Additional experiments will involve the study of myocardial cell integrity in acute myocardial infarction.